In the fabrication of semiconductor integrated circuit (IC) devices, various device features such as insulation layers, metallization layers, passivation layers, etc., are formed on a semi-conducting substrate. It is known that the quality of an IC device fabricated is a function of the processes in which these features are formed. The yield of an IC fabrication process is in turn a function of the quality of the device fabricated and a function of the cleanliness of the manufacturing environment in which the IC device is processed.
The ever increasing trend of miniaturization of semiconductor IC devices occurring in recent years requires more stringent control of the cleanliness in the fabrication process or the processing chamber in which the process is conducted. This leads to a more stringent control of the maximum amount of impurities and contaminants that are allowed in a process chamber. When the dimension of a miniaturized device approaches the sub-half-micron level, even a minutest amount of contaminants can significantly reduce the yield of the IC manufacturing process. For instance, the yield of the process can be drastically reduced by the presence of contaminating particles during deposition or etching of films which leads to the formation of voids, dislocations or short-circuits resulting in performance and reliability problems in the IC devices fabricated.
In recent years, contamination caused by particles or films has been reduced by the improvements made in the quality of clean rooms and by the increasing utilization of automated equipment which are designed to minimize exposure to human operators. However, even though contaminants from external sources have been r educed, various contaminating particles and films are still generated inside the process chamber during processing of semiconductor wafers. Some possible sources of contamination that have been identified include the process gases and liquids, the interior walls of the process chambers and the mechanical wear of the wafer handling equipment.
The chances of generating contaminating particles are also increased in process chambers that are equipped with plasma enhancement. Various chemically reacted fragments are generated from the processing gases which include ions, electrons and radicals. These fragments can combine and form negatively charged particles which may ultimately contaminate a substrate that is being processed in the chamber. Various other materials, such as polymeric films may be coated on the process chamber walls during plasma processing. The films may dislodge and fall from the process chamber walls when subjected to mechanical and thermal stresses onto the wafers that are being processed in the chamber.
Conventionally, a wet cleaning process must be conducted in a semiconductor process chamber as part of a preventive maintenance schedule. For instance, in a chemical vapor deposition (CVD) chamber, a preventive maintenance schedule which included a wet cleaning is conducted on a monthly basis. The wet cleaning process can be carried out by using cleaning solvents such as IPA (isopropyl alcohol), deionized water, IPA/deionized water mixture, or the more volatile acetone. A wet cleaning process is time consuming and generally hazardous to a maintenance personnel who carries out the process due to the toxic nature of the residual reactant gases, the reaction by-products and the cleaning solvent used. For instance, in a wet cleaning process for a chemical vapor deposition chamber that was utilized for depositing tungsten plugs, the cleaning procedure must be carefully carried out due to the toxic nature of tungsten fluoride reactant gas used in the chamber and the possibility of encountering residual reactant gas during the cleaning process.
Similarly, in a process chamber for depositing high temperature films (HTF), highly toxic reactant gases are also used which make the chamber cleaning process a hazardous task. In these process chambers, the contaminating substances may be in the form of either particulates or fumes. For instance, in a semiconductor process chamber, the particulate sources may include silicon dust, quartz dust, atmospheric dust, and particles originating from clean room personnel and processing equipment. Some of the examples of fume contaminants are solvent residues such as from acetone, isopropyl alcohol, methyl alcohol, xylene, photoresist developer residues from dissolved photoresist materials, oil fumes introduced through improperly filtered air or gas lines, metallic etchant or photoresist strip baths.
In a conventional process for wet cleaning a process chamber, a ventilation hood that is made of an opaque or metallic material is placed over an open process chamber for ventilation of the toxic or hazardous fumes from the process chamber. The ventilation hood is normally connected to a facility vacuum source such that hazardous fumes are exhausted away from the maintenance personnel for safety reasons. A typical wet cleaning process can be carried out in the following manner. In a monthly preventive maintenance procedure conducted in a CVD chamber for tungsten plugs, a ventilation hood is first placed on top of an open process chamber which is connected to a facility vacuum for a time period of at least one hour to evacuate the hazardous fumes in the process chamber. After the evacuation time of at least one hour, or preferably between one and two hours, a wet cleaning of the chamber is conducted by using a cleaning solvent such as IPA. To improve the cleaning efficiency, an air gun is used simultaneously during the evacuation process by the facility vacuum to blow dry nitrogen into the chamber cavity such that contaminating particles or films may be dislodged from the chamber walls and be evacuated away by the facility vacuum. In order to blow dry nitrogen into the chamber cavity, an access door must be provided in the hood body such that a maintenance personnel may operate an air gun through the access door to reach inside the chamber cavity. This is both a time consuming and hazardous task for the operator due to the danger of possible exposure to any toxic components in the exhausted fumes, even though the process is essential before a wet cleaning can be carried out.
It is therefore an object of the present invention to provide a ventilation hood for use in cleaning a process chamber that does not have the drawbacks or shortcomings of the conventional ventilation hoods.
It is another object of the present invention to provide a ventilation hood equipped with an access door for cleaning a process chamber that does not require the manual operation of an air gun inside the hood by an operator and thereby eliminating the risk of exposure to hazardous components of the exhaust.
It is a further object of the present invention to provide a ventilation hood that can be used effectively to remove hazardous fumes and contaminating particles from a process chamber prior to conducting a wet cleaning process on the chamber.
It is another further object of the present invention to provide a ventilation hood for use in cleaning a process chamber prior to a wet cleaning process that is constructed of a substantially clear material such that the cleaning process can be visually observed.
It is yet another object of the present invention to provide a ventilation hood that is equipped with an access door such that the maintenance of accessories inside a process chamber can be carried out if necessary.
It is still another object of the present invention to provide a ventilation hood for use in cleaning a process chamber that is equipped with a fluid flow channel system and fluid nozzles inside the hood.
It is still another further object of the present invention to provide a ventilation hood for use in cleaning a process chamber that is equipped with a fluid flow channel and fluid nozzles inside the hood such that a purge gas can be flown through the hood and the process chamber to carry away contaminating particles.
It is yet another further object of the present invention to provide a method for venting a process chamber prior to a wet cleaning process by flowing into the hood and the process chamber a purge gas simultaneously with the vacuum evacuation process such that substantially all contaminating particles are removed from the chamber.